Technical Field
The present disclosure relates to a liquid crystal display device, including particularly a liquid crystal display device capable of minimizing misalignment between a bottom plate and a liquid crystal display panel for implementing a narrow bezel.
Description of the Related Art
Liquid crystal display (LCD) devices are one of the most prevalent display devices. A liquid crystal display adjusts the amount of transmitted light by applying a voltage across the electrodes to re-orient liquid crystal molecules in the liquid crystal layer.
A typical liquid crystal display device includes a liquid crystal display panel displaying images and a backlight unit providing light to the liquid crystal display panel. In addition, a liquid crystal display device further includes a bottom plate accommodating the liquid crystal display panel and the backlight unit. Typically, the bottom plate has a box shape with an open top. The backlight unit includes elements, such as a light source, a light guide plate, a reflective plate, and a plurality of optical sheets, and the backlight unit is disposed in the bottom plate. The liquid crystal display panel is disposed on the backlight unit, such that the backlight unit and the liquid crystal display panel are surrounded by side walls of the bottom plate. Accordingly, when viewed from the top of the liquid crystal display panel, a part of the bottom plate, particularly the side walls may be seen. To avoid the bottom plate from being seen by viewers, a shielding layer is disposed on a cover glass on the liquid crystal display panel. The shielding layer has at least a width sufficient to hide the part of the bottom plate which is not covered by the liquid crystal display panel.
Recently, there is an increasing demand for liquid crystal display devices that have better designs and aesthetics, in addition to functionality, such as image quality, response speed and contrast ratio.
Accordingly, the demand for liquid crystal display devices having a narrow bezel (minimal bezel or zero bezel) is increasing. Such devices are light and thin and have as large a display area and as a small non-display area, i.e., bezel area, as possible.
However, when the shielding layer is disposed on the cover glass to shield the side walls of the bottom plate from viewers as described above, the shielding layer should be at least wide enough to hide the side walls. Thus, there is a limit to implementing a desirable narrow bezel structure.
There are several ways to implement a narrow bezel. For example, one option would be to equalize the area of the bottom plate and the area of the lower surface of the liquid crystal display panel. Specifically, the bottom plate accommodates the backlight unit, and the liquid crystal display panel is disposed on the side walls of the bottom plate, to minimize the width of the shielding layer on the cover glass. That is, when viewed from the top or front of the liquid crystal display panel, the liquid crystal display panel is disposed on the side walls of the bottom plate such that the bottom plate is hidden by the liquid crystal display panel. In the liquid crystal display device having the above-described structure, the width occupied by the shielding layer to shield the bottom plate from viewers viewing the device from the top (or front) can be reduced, thereby implementing a narrow bezel.
In fabricating a liquid crystal display device having the above-described structure, a process of disposing the liquid crystal display panel on the side walls of the bottom plate requires accurate alignment of the bottom plate with the liquid crystal display panel. Generally, the liquid crystal display panel is surrounded by the side walls of the bottom plate, and thus the liquid crystal display panel can be inserted into the bottom plate without aligning the two layers. However, in fabricating a liquid crystal display device where the liquid crystal display panel is disposed on the side walls of the bottom plate, an alignment process is necessary to accurately place the liquid crystal display panel at the desired location. If there is misalignment between the bottom plate and the liquid crystal display panel, the backlight unit is not in line with the liquid crystal display panel, and light leakage may occur from the backlight unit, thereby degrading the image quality.
In this regard, a method for disposing a liquid crystal display panel on the bottom plate has been proposed, in which an alignment hole is formed in the bottom plate, an alignment mark is formed on the liquid crystal display panel, and the bottom plate is aligned with the liquid crystal display panel such that the alignment mark is in line with the alignment hole.
However, the alignment mark and the alignment hole may be misaligned due to the material and structure of the bottom plate.
For example, the bottom plate may be made of a metallic material such as stainless steel (SUS). When the bottom plate is made of a metallic material, the light produced by the backlight unit is reflected off the bottom plate resulting in light leakage. To address this problem, a mold made of a plastic material may be disposed on the inner periphery of the bottom plate. Such a mold is made of a light-absorbing material and thus, can suppress light leakage. The alignment hole formed in the bottom plate may penetrate the mold.
On the other hand, irregularities (e.g. burrs) or uneven surface portions may be formed on the inner surface of the mold during the process of forming the alignment hole by penetrating the mold, because the mold is made of a plastic material, and the inner surface of the mold surrounding the alignment hole is not smooth. In addition, the shape of the inner surface of the mold surrounding the alignment hole may differ from that of another alignment hole.
As described above, the shape of the alignment hole is changed or blocked due to burrs or irregular surfaces inside the alignment hole, or the shape of the alignment hole is not uniform. As a result, the bottom plate and liquid-crystal display panel may be misaligned during the alignment process using the alignment hole and the alignment mark.